Production of mixed crystals of sodium glutamate and sodium inosinate

ABSTRACT

MIXED CRYSTALS OF SODIUM GLUTAMATE AND DISODIUM INOSINATE ARE PREPARED BY ADDING A SOLUTION CONTAINING BOTH MONODIUM GLUTAMATE AND DISODIUM INOSINATE TO A MONOSDIUM GLUTAMATE MOTHER LIQUOR CONTAINING SEED CRYSTALS OF MONOSODIUM GLUTAMATE, AND SIMULTANEOUSLY EVAPORATING THE RESULTING MIXTURE TO GROW MIXED CRYSTALS OF A DESIRED SIZE.

9, 1973 HIROTOSHI SAMEJIMA ETAL 3,70

PRODUCTION OF MIXED CRYSTALS 0F SODIUM GLUTAMATE AND SODIUM INOSINATE Original Filed April 4, 1967 o/soolum IIVOS/Nfl TE 72 4/ 0 /1 E g Q 100 200 300 40? 5&0 molvosoolum Gu/mma 175 g/l 50/. UBlL/TY CURVE 0F MONOSUD/UM GLUTHMH TE- DISOD/UM lA/05/Mq r5 fi fi a nv wars/2 A7 21C.

. INVENTOES Hwo 705/4! SAMEJ MA 4mm fi/eum ks/J/ Smnmam 14 TTOKNE Y5 United States Patent Int. Cl. A231 1/26 U.S. Cl. 99-140 N 4 Claims ABSTRACT OF THE DISCLOSURE Mixed crystals of sodium glutamate and disodium inosinate are prepared by adding a solution containing both monosodium glutamate and disodium inosinate to a monosodium glutamate mother liquor containing seed crystals of monosodium glutamate, and simultaneously evaporating the resulting mixture to grow mixed crystals of a desired size.

This application is a continuation of SN. 628,478, Apr. 4, 1967, now abandoned.

BACKGROUND OF THE INVENTION The present invention is concerned with a process for producing mixed crystals of monosodium glutamate and disodium inosinate. According to the present invention, mixed crystals of sodium glutamate and sodium inosinate, which have excellent appearance and in which disodium inosinate is dispersed in any desired ratio, can be produced without the formation of monocrystals of sodium inosinate by feeding a solution containing both sodium glutamate and sodium inosinate as an accelerator for the growth of seed crystals of sodium glutamate, even using apparatus conventionally employed for producing crystals of sodium glutamate.

As a result of technical developments in the preparation of inosinic acid, guanylic acid etc., an increasing demand for mixed seasonings containing such flavor-enhancing agents and sodium glutamate has recently been created because of their synergistic effects.

For the purpose of producing composite flavor-enhancing substances containing sodium glutamate and sodium inosinate, it is known to mix mechanically crystals of sodium glutamate with those of sodium inosinate, or alternatively to form coating layers of sodium inosinate on the surfaces of crystals of sodium glutamate by applying and drying a concentrated solution of sodium inosinate on the surfaces of sodium glutamate crystals. However, the former mixing process has the disadvantages of poor uniformity of the products obtained, and the latter process has the disadvantages of injuring the beautiful appearance, which may characterize crystals of sodium glutamate. In addition, both processes may require various pieces of equipment specifically designed for carrying them out.

With a view toward achieving composite enhancing or seasoning materials of beautiful appearance and uniform quality containing sodium glutamate and sodium inosinate 3,709,701 Patented Jan. 9, 1973 without using any apparatus specifically designed for this purpose, we have conducted research with respect to processes for the production of mixed crystals of sodium glutamate and sodium inosinate, which may be carried out even in conventional apparatus for the production of crystals of sodium glutamate, itself, and have discovered the process according to the present invention, which accomplishes these objects with a good yield based on the starting materials.

As a result of extensive study in the production of mixed crystals of sodium glutamate and sodium inosinate, we have observed that mixtures of the two materials exhibit the solubility curve shown in the accompanying drawing, bearing out the assumption that the salting out effect may decrease the solubilities of the substances in the mixed solution. Based on this observation, we conceived the possibility of producing mixed, crystals of monosodium glutamate and disodium inosinate economically by using even apparatus conventionally used for crystallizing sodium glutamate, and this finding may open up an economical reuse of the mother liquor in practice.

In addition, it has also been found that normal growth of seed crystals can with advantage be achieved by the addition of sodium inosinate to the mother liquor after seed crystals of sodium glutamate have been caused to be present in the mother liquor by formation therein or addition thereto. Otherwise, it is difficult to achieve an advantageous growth of seed crystals in the mother liquor.

SUMMARY OF THE INVENTION Mixed crystals of sodium glutamate and disodium inosinate are prepared by adding a solution containing both monosodium glutamate and disodium inosinate to a monosodium glutamate mother liquor containing seed crystals of monosodium glutamate, and simultaneously evaporating the resulting mixture to grow mixed crystals of a desired size.

The seed crystals may be caused to be present in the original mother liquor either by evaporating a solution of monosodium glutamate until seed crystals are spontaneously formed and have grown to a size which will not pass through a mesh screen, or a suitable number of separately formed seed crystals of this size can be added to a mother liquor saturated with monosodium glutamate.

The solution containing both monosodium glutamate and disodium inosinate in the desired ratio with from 250-500 mg./ml. of monosodium glutamate being present is added either continuously or intermittently to mother liquor containing the seed crystals while simultaneously concentrating the resulting mixture. The concentration is carried out in such a manner that no ad ditional seed crystals are formed, and the mixed crystals are grown until they reach the desired size. Ordinarily, culturing is continued for about 6-10 hours.

The mixed crystals formed are then harvested and they have an excellent appearance comparable to that of monocrystals of monosodium glutamate. The mixed crystals are uniform from the nucleus to the surface as to the relative proportions of monosodium glutamate and disodium inosinate.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing depicts the solubility curve in water at 21 C. of a monosodium glutamate-disodium inosinate system.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS The process according to the present invention will now be explained in detail.

Seed crystals of sodium glutamate are in general obtained in a suitable crystallizer having an agitator capable of agitating at slow speed, such as e.g. a vacuum evaporation type crystallizer in which a mother liqwor of monosodium glutamate is concentrated at 35-85 C., preferably at 50-70 C., under reduced pressure to a range of 600-750 mg./ml. preferably 640 700 mg./ml., thereby to form spontaneously a suitable number of seed crystals of monosodium glutamate therein. Alternatively, it is also possible to add to the mother liquor in saturated state a suitable number of seed crystals.

To the mother liquor, containing seed crystals, continously or intermittently, with continuous stirring and while continuing concentration, there is added a solution, which contains about 250-500 mg./ml. of monosodium glutamate and a desired concentration of disodium inosinate, whereby both monosodium glutamate and disodium inosinate crystallize out as mixed crystals around said seed crystals or nuclei. The mixed crystals thus formed contain both substances uniformly at a desired ratio and have a beautiful appearance similar to that of monosodium glutamate crystals.

The mixed crystals thus formed are cultured e.g. for

-l hours to obtain the desired sizes and are then harvested.

According to the present invention, the concentration level of the mixed solution containing monosodium glutamate and disodium inosinate should be kept within the range as described above to prevent formation of seed crystals in addition to those originally present. (Furthermore, the size of the seed crystals before the addition of disodium inosinate should be such that they will not pass through a 150 mesh screen. Otherwise, various difficulties arise in the advantageous growth of seed crystals. It is essential therefore, in the case of the spontaneous formation of seed crystals in the mother liquor, to add the solution containing disodium inosinate and monosodium glutamate to the mother liquor at such a time that the growth of seed crystals to a size such that they will not pass through a 150 mesh screen has already been accomplished, while seed crystals having desired mesh sizes can easily be employed in the case of the addition of seed crystals to the mother liquor.

According to the present invention, there are obtained mixed crystals of monosodium glutamate and disodium inosinate, which have a beautiful appearance similar to that of monosodium glutamate crystals and which also contain both substances uniformly at any desired ratio, by providing the mother liquor with a suitable number of seed crystals, continuing the concentration of the mother liquor in such a manner that no additional seed crystals might be formed spontaneously therein, adding to the mother liquor continuously or intermittently a mixed solution, which contains about 250-500 mg./ml. of monosodium glutamate and a desired concentration of disodium inosinate, thereby to form mixed crystals, and culturing the formed seed mixed crystals until desired mesh sizes can be obtained. The cultivation is for example preferably continued for about 6-10 hours.

It has been found that about 35% of the monosodium glutamate and disodium inosinate remain in the mother liquor and about 65% can be crystallized as mixed crystals.

In order to achieve better results, it is important that seed crystals having sizes larger than those of crystals which will just pass through a 150 mesh screen are added to the mother liquor, or may be formed therein and that thereafter a mixed solution containing both substances uniformly should be added to the mother liquor for the formation of mixed crystals.

4 EXAMPLE 1 1,630 g. of glutamac acid (purity-98%) and 7,000 ml. of water are mixed with 435 g. of sodium hydroxide and thoroughly stirred. The solution, to which is added 5 0 g. of active carbon, is heated at 60 C. for one hour with stirring and is then filtered. Separated carbon is washed with water and the washing is combined with the filtrate. Thus, 8,000 ml. of an original solution (concentration-250 g./ 1.) of decolorized and purified monosodium glutamate is obtained.

In a separable flask, 4,000 ml. of the glutamate solution is concentrated to 1,600 ml. and 100 g. of mesh seed crystals are added to the concentrate. Then, the concentration in vacuo is carried out at an evaporation rate of 500 ml./hour. 50 grams of disodium inosinate is dissolved in the remaining 4,000 ml. of the original solution and the solution is fed continuously to the concentration system at a rate of 520 ml./hour. Just after the completion of the feeding, the concentrate is removed and is centrifuged. The thus obtained mixed crystals are dried to yield 1,400 g. of dried crystals (water content0.l5%). Their appearance and luster are observed to be similar to those of monosodium glutamate crystals. The crystals having mesh sizes of 50-60 are dissolved and analyzed and are observed to contain almost equal ratios of disodium inosinate. Moreover, crystals, after washing slightly with warm water are also observed to contain almost equal ratios of disodium inosinate. The amounts of monosodium glutamate and disodium inosinate in the total crystals are respectively 1,365 g. and 33 g. The yields are respectively 65% and 66%. The content of disodium inosinate in the crystals is 2.36%.

EXAMPLE 2 In a manner similar to that described in "Example 1, 1 0,000 ml. (concentration-200 g./l.) of an original solution of monosodium glutamate is obtained by neutralizing glutamic acid with caustic soda and is decolorized with active carbon. 5,000 ml. of the original solution are concentrated to 1,500 ml. in a separable flask at 50 C. and there are added 100 grams of seed crystals of about 140 mesh size. Then, the solution is concentrated in vacuo at an evaporation rate of 700 ml./hour. 110 grams of disodium inosinate are dissolved in the remaining 5,000 ml. of the original solution and the resulting solution is fed continuously to the concentration system at a rate of 710 ml./hr. for the growth of seed crystals. Just after the completion of feeding, the concentrate is centrifuged. The separated crystals are dried to give 1,444 g. of dried crystals (water content 0.14%). No difference from usual sodium glutamate crystals is observed as to appearance of form and luster. The amount of monosodium glutamate in the crystals is 1,370 g. and that of disodium inosinate is 72 g. The inosinate content is 5%. Crystals having a size of 50-60 mesh are analyzed as to the inosinate content, and it is found that the crystals contain almost equal ratios of disodium inosinate, and that the portions of crystals, which remain after being washed slightly with warm water, also contain disodium inosinate. The yields of the crystallized monosodium glutamate and disodium inosinate are both 65%.

We claim:

1. A process for producing mixed crystals of monosodium glutamate and disodium inosinate, comprising adding continuously or intermittently a solution containing both monosodium glutamate in an amount of about 250500 mg./ml., and disodium inosinate to a mother liquor or monosodium glutamate containing seed crystals consisting of monosodium glutamate of a size such that they will not pass through a mesh, and simultaneously evaporating said mother liquor to cause the seed crystals to grow in such a manner that no additional seed crystals or nuclei are formed therein after addition of said solution containing both monosodium glutamate and disodium inosinate is begun.

2. A process as claimed in claim 1 in which prior to References Cited addition of said solution, the mother liquor is concen- UNITED STATES PATENTS trated at 3585 C. under reduced pressure to a concentration within the range of 600-750 mg./ml. whereby 2,584,731 2/1952 Ogawa 9916 seed crystals are spontaneously formed. 5 FOREIGN PATENTS 3. A process as claimed in claim 2 in which said mother liquor is concentrated to a concentration within 1397711 3/1965 France 99*140 the range of 640700 MORR IS O. WOLK, Primary Examiner 4. A process as claimed in claim l in which the mixed crystals formed are grown for 6-10 hours. 10 BOVEE Assistant Exammer 

